Method for regenerating calcium sulfoxy compounds produced in the combustion of carbonaceous fuels in fluidized beds

Abstract

In methods for combusting carbonaceous sulfur-containing fuels in a fluidized bed wherein the fluidized bed contains at least one calcium compound selected from the group consisting of calcium oxide, calcium hydroxide, calcium carbonate and calcium bicarbonate to absorb sulfur oxides formed during the combustion of the carbonaceous fuel thereby producing calcium sulfoxy compounds having the formula CaSO x wherein x is 3 or 4, an improvement comprising (a) withdrawing a stream of fluidized bed solids containing said calcium sulfoxy compounds and mixing the fluidized bed solids and said calcium sulfoxy compounds with water to produce a slurry; (b) reacting the CaSO x compounds with NH 3 , H 2 O and CO 2 to produce water-soluble ammonium sulfoxy compounds such as NH 4 (HSO x ) where x is 3 or 4 and CaCO 3 ; and (c) separating the ammonium sulfoxy compounds from the fluidized bed solids and CaCO 3 .

Having thus described the invention, I claim: 
     
       1. In a method for combusting carbonaceous sulfur-containing fuels in a fluidized bed wherein said fluidized bed contains at least one calcium compound selected from the group consisting of CaO, Ca (OH) 2 , CaCO 3  and Ca(HCO 3 ) 2  to absorb sulfur oxides formed during combustion of said carbonaceous fuel to produce calcium sulfoxy compounds having the general formula CaSO x  wherein x is 3 or 4 the improvement comprising: (a) withdrawing a stream of fluidized bed solids containing said CaSO x  and mixing said fluidized bed solids with water to produce a slurry;   (b) reacting said CaSO x  in said slurry with NH 3 , H 2  O and CO 2  to produce watersoluble ammonium sulfoxy compounds and CaCO 3  ;   (c) separating said water-soluble ammonium sulfoxy compounds from said fluidized bed solids and said CaCO 3  ;   (d) recycling at least a portion of said CaCO 3  to said fluidized bed.   (e) reacting said water-soluble ammonium sulfoxy compounds with H 2  S at a temperature from about 300° to about 600° F. and a pressure from about 150 to about 2000 psig to produce ammonium polysulfide;   (f) thermally decomposing said ammonium polysulfide at a temperature from about 200° to about 300° F. to produce NH 3 , H 2  S and sulfur;   (g) recycling said NH 3  to step (b) to the reaction of said CaSO x  with NH 3 , H 2  O and CO 2  ;   (h) recycling said H 2  S to step (e) to the reaction of said water-soluble ammonium sulfoxy compounds with H 2  S; and,   (i) recovering at least a portion of said sulfur.   
     
     
       2. The improvement of claim 1 wherein said water-soluble ammonium sulfoxy compounds comprise at least one of NH 4  HSO x  and NH 4  (SO x ) 2  where x is 3 or 4. 
     
     
       3. In a method for combusting carbonaceous sulfur-containing fuels in a fluidized bed wherein said fluidized bed contains at least one calcium compound selected from the group consisting of CaO, Ca(OH) 2 , CaCO 3 ) 2  to absorb sulfur oxides formed during combustion of said carbonaceous fuel to produce calcium sulfoxy compounds having the general formula CaSO x  wherein x is 3 or 4 the improvement comprising: (a) withdrawing a stream of fluidized bed solids containing said CaSO x  and mixing said fluidized bed solids with water to produce a slurry;   (b) reacting said CaSO x  in said slurry with NH 3 , H 2  O and CO 2  to produce water-soluble ammonium sulfoxy compounds and CaCO 3  ; and   (c) separating said water-soluble ammonium sulfoxy compounds from said fluidized bed solids and said CaCO 3  ;   (d) recycling at least a portion of said CaCO 3  to said fluidized bed;   (e) reacting said water-soluble ammonium sulfoxy compounds with a carbonaceous solid at a temperature from about 1200° to about 1600° F. and a pressure from about 0 to about 250 psig to produce NH 3 , H 2  S and carbon oxides; and,   (f) recycling said NH 3  to step (b) to the reaction of said CaSO 4  with NH 3 , H 2  O and CO 2 .   
     
     
       4. The improvement of claim 3 wherein said H 2  S is passed to sulfur recovery. 
     
     
       5. The improvement of claim 3 wherein said water-soluble ammonium sulfoxy compounds comprise at least one of NH 4  HSO x  and NH 4  (SO x ) 2  wherein x is 3 or 4.